A step in the making of cement is the grinding of the cement clinker. Since cement clinkers are very hard, the fragmentation is very energy-intensive. It can be desirable for the properties of the cement that it be present as a fine powder. Therefore, the fineness of the cement can be a quality feature of interest. In order to facilitate the fragmenting into powder form, so-called cement grinding aids are used. In this way, the grinding times and energy costs are greatly reduced.
Organic amines with a molecular weight Mw of less than 500 g/mol, or their ammonium salts, are widespread grinding aids. Examples of such organic amines are alkanolamines such as trialkanolamines, triisopropanolamine (TIPA) or triethanolamine (TEA). However, they can have the drawback that, after a certain quantity, they accelerate the start of the stiffening, or the time difference between the end of solidification and the beginning of solidification, i.e., they act as accelerators.
In order for aqueous hydraulic binding agents to be workable for a longer time, binding retardants are added, also known hereafter as retardants, in order to drag out the onset of stiffening, or increase the time difference between the end of solidification and the beginning of solidification. The adding of these retardants to the hydraulic binding agents can be done with the adding of the mixing water or shortly thereafter.
Another problem of grinding aids is that they can promote brown discolorations of the set hydraulic binding agents. There is relatively little reliable data as to the influence of grinding aids on the formation of brown discolorations (Reducing the risk of brown discoloration of concrete objects, Härdtl et al, BFT Betonwerk+Fertigteil-Technik, No. 11, 2003, pages 34-46, Bauverlag).